// $Id: HandlerStack.java 1153 2008-11-30 16:14:45Z bobtarling $
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package org.tigris.gef.persistence.pgml;

import org.xml.sax.helpers.DefaultHandler;

/**
 * A class that implements this interface is responsible for maintaining the
 * stack of ContentHandler objects in response to {@link #pushHandlerStack} and
 * {@link #popHandlerStack} calls, and for making sure that the SAX parser is
 * always using the ContentHandler object at the top of the stack.
 * 
 * @author Michael MacDonald
 */
public interface HandlerStack {
    /**
     * Pushes a new ContentHandler on the stack and insures that the SAX parser
     * uses that handler for further events.
     * 
     * @param handler
     *                ContentHandler to be pushed on the handler stack
     */
    void pushHandlerStack(DefaultHandler handler);

    /**
     * Removes the top handler from the stack and insures that the SAX parser
     * calls the previously underlying, now top ContentHandler object for
     * further events.
     */
    void popHandlerStack();
}
